Twin-Twin Transfusion Syndrome

What is Twin-Twin Transfusion Syndrome (TTTS)?

Identical twins that share a common placenta (monochorionic twins) usually have blood vessel connections between the two fetuses. In about 15% of these pregnancies, twin-twin transfusion syndrome (TTTS) occurs when these blood vessels produce an imbalance or uneven sharing of the blood. As a result, blood from one twin (the "donor twin") is pumped to the other twin (the "recipient twin"). When this occurs, the heart of the donor twin must do extra work to support the recipient twin. The recipient twin gets too much blood and the donor twin does not get enough.

This unequal sharing of blood causes problems for both babies. The amniotic fluid level can be high for the recipient twin and low for the donor twin. Blood flow is going away from the donor twin who may become anemic (have a low blood count). The recipient twin can develop heart failure from having the burden of pumping extra blood. This may cause increased fluid to build up in the fetus that can lead to fetal death.

If left untreated, one or both twins may die. Because there are blood vessel connections in the placenta between the fetuses, one twin can be affected by death of the other twin. There is an increased risk of neurological complications or death in the remaining twin.

Once the condition has been detected, a targeted ultrasound will be performed to rule out the presence of additional anomalies in the twins. Amniocentesis may be recommended to look for chromosomal abnormalities and a specialized ultrasound of the fetal hearts, called an echocardiogram, may also be performed. TTTS is a progressive disease in which mild cases require only careful monitoring of twin growth and amniotic fluid. Severe cases in which one or both twins appear to be in danger may require fetal intervention.

Note: The patient education videos are intended to provide families with objective information about their diagnosis. The information presented in these videos is educational and is intended to develop a general knowledge of the condition and/or procedure. It is not intended as medical advice or the practice of medicine. Specific aspects of your condition, expected outcomes, and care should be addressed and answered after consultation with your physician. Not all affiliated physicians are Memorial Hermann employees.

Will fetal treatment be required?

Not every pregnancy with this condition will require fetal treatment. If it is determined that fetal intervention is the best option for your pregnancy, the team at the Center will develop a comprehensive plan for you and your babies during and after birth. All patients that have been diagnosed with TTTS should learn about potential fetal interventions. There are several treatment options available. Based on the severity of the case, your doctors at the Center will recommend the most appropriate treatment option.

Serial Amnioreduction - Amnioreduction involves removing excessive amniotic fluid from the enlarged sac. This procedure has been used to reduce the risk of membrane rupture, improve maternal discomfort, and prolong the pregnancy. Since amniotic fluid can re-accumulate after removal, the procedure usually needs to be repeated several times. Some physicians believe that amnioreduction increases survival compared to no fetal intervention.

Laser ablation - Laser ablation treatment involves identifying the vessels that connect the two fetuses and interrupting the blood flow in these vessels using a laser. The procedure requires insertion of a small camera (fetoscopy) and laser device to coagulate the vessels that are abnormally connected. Survival with this procedure has been reported to be as high as 85% for one twin and 60% for both. Neurological complications have been reported in about 10% of survivors.

The procedure is typically performed under regional (epidural or spinal) anesthesia. Afterwards, the mother will be admitted to the Women's Center at Children's Memorial Hermann Hospital to closely monitor the pregnancy. Medications and bed rest may be prescribed to minimize the risk of preterm labor. After discharge, mothers will continue to be followed by the Center and your obstetrician for ongoing care.

What special considerations should be made for delivery?

Type of delivery - The delivery plan will be carefully discussed with you and your obstetrician.

Place of delivery - If all of the prenatal monitoring suggests that your pregnancy is going well, the twins can be delivered at the hospital of your choice. However, the hospital should be prepared to handle any additional needs of your newborns and have a neonatal intensive care unit with the capability to provide specialized care.

Time of delivery - There is no reason to intentionally induce an early delivery. As long as the fetuses and mother are stable, the pregnancy should be allowed to proceed to term. If the twins' condition deteriorates, earlier delivery may be necessary.

What will happen at birth?

Immediately following delivery, doctors will carefully evaluate and begin treatment if necessary. Most infants will be born without any problems. You and your loved ones should be able to immediately hold and bond with your newborns. If needed the babies will be stabilized in an intensive care unit and treated by the neonatologists (specialists in the care of high-risk newborns).

What are the long-term outcomes and considerations?

Complicated twin / multifetal pregnancies will be followed for any signs or symptoms of neurologic complications. The multidisciplinary team at the Center will evaluate which treatment option is best for you and your pregnancy. If longterm follow up with a pediatric specialist is required, the clinic coordinators will help each family bridge the gap, connecting families with the specialists.

Note: This information regarding your condition is meant to be a helpful, informative introduction. Because every newborn is different, this may not be applicable to all cases, especially if there are additional defects. Your team of experts at the Center will provide you with information specific to your pregnancy.

Contact Us

To contact Children's Memorial Hermann Hospital, please fill out the form below.

Many physicians affiliated with Children’s Memorial Hermann Hospital are faculty at McGovern Medical School at UTHealth. The affiliated physicians from McGovern Medical School consults with patients at UT Physicians clinic with all advanced treatments provided at Children’s Memorial Hermann Hospital.